TECHNIQUES FOR 40 MEGAHERTZ (MHz) CHANNEL SWITCHING

ABSTRACT

Embodiments of the invention include methods, articles, and apparatuses to provide information related to channels transmitted and received according to a wireless communications protocol. One embodiment of the invention provides a method comprising generating channel offset information corresponding to an extension channel within a channel of a wireless communications protocol, and transmitting the channel offset information as part of channel information to be transmitted to one or more remote devices communicating according to the wireless communications protocol. Other embodiments are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication No. 60/775,135 filed on Feb. 18, 2006.

TECHNICAL FIELD

Embodiments of the invention relate to wireless communications. Moreparticularly, embodiments of the invention relate to wireless local areanetwork (WLAN) communications utilizing 40 MHz channel switchingincluding, for example, IEEE 802.11n based communications.

BACKGROUND

Current Institute of Electrical and Electronics Engineers (IEEE)802.11b/g wireless local area network (WLAN) standards offer theconvenience of wireless connections with adequate performance for manytasks. The IEEE 802.11b standard corresponds to IEEE Std. 802.11b-1999entitled “Local and Metropolitan Area Networks, Part 11: Wireless LANMedium Access Control (MAC) and Physical Layer (PHY) Specifications:Higher-Speed Physical Layer Extension in the 2.4 GHz Band,” approvedSep. 16, 1999 as well as related documents. The IEEE 802.11g standardcorresponds to IEEE Std. 802.11g-2003 entitled “Local and MetropolitanArea Networks, Part 11: Wireless LAN Medium Access Control (MAC) andPhysical Layer (PHY) Specifications, Amendment 4: Further Higher RateExtension in the 2.4 GHz Band,” approved Jun. 27, 2003, as well asrelated documents. Related documents may include, for example, the IEEE802.11a standard.

However, for some operations under current WLAN standards, such asstreaming high quality multimedia content, throughput provided by thesestandards may not be adequate. In response to demand, IEEE approved thecreation of the IEEE 802.11 Task Group N (TGn) to define modificationsto the Physical Layer and Medium Access Control Layer (PHY/MAC) todeliver 100 megabit-per-second (Mbps) or greater throughput. The resultis an upcoming specification referred to as ‘IEEE 802.11n’ that is anaddition to the 802.11 family of standards that is intended to increasewireless network speed and reliability.

IEEE 802.11n communications are based on multiple input, multiple output(MIMO) technology that uses multiple antennae at both the transmitterand receiver sides of a communication link. The 802.11n standard may useorthogonal frequency-division multiplexing (OFDM) to increase speed, aswell as techniques to transmit multiple redundant copies of data toincrease reliability. With prior art standards, a 20 MHz channelbandwidth was utilized. However, MIMO approaches using only 20-MHzchannel require higher implementation costs to meet the IEEE TGnrequirement of 100 Mbps throughput. Meeting the IEEE TGn requirementwith only 20-MHz channels would require at least three antenna analogfront ends at both the transmitted and receiver. At the same time, a20-MHz approach will struggle to provide a robust experience withapplications that demand higher throughput in real user environments.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are illustrated by way of example, and notby way of limitation, in the figures of the accompanying drawings inwhich like reference numerals refer to similar elements.

FIG. 1 illustrates a block diagram of one embodiment of a wireless localarea network;

FIG. 2 illustrates one embodiment of a New Extension Channel Offsetelement;

FIG. 3 is a conceptual illustration of one embodiment of a channelswitch request primitive;

FIG. 4 is a conceptual illustration of one embodiment of a channelswitch indication primitive; and

FIG. 5 is a conceptual illustration of one embodiment of a channelswitch response primitive.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth.However, embodiments of the invention may be practiced without thesespecific details. In other instances, well-known circuits, structuresand techniques have not been shown in detail in order not to obscure theunderstanding of this description.

Reference in the specification to “one embodiment” or “an embodiment”means that a particular feature, structure, or characteristic describedin connection with the embodiment is included in at least one embodimentof the invention. The appearances of the phrase “in one embodiment” invarious places in the specification are not necessarily all referring tothe same embodiment.

Embodiments of the invention provide for 40 MHz channel switching inwireless local area network (WLAN) communications, such as in IEEE802.11n based communications. In one embodiment, a 40 MHz channel mayinclude both control and extension channels (each 20 MHz). To implement40 MHz channel switching, described herein are an Extension Channelinformation element and a format for a Channel Switch Announcementframe.

It should be understood that embodiments of the present invention may beused in a variety of applications. Although the present invention is notlimited in this respect, the circuits disclosed herein may be used inmany apparatuses such as in the transmitters and receivers of a radiosystem. Radio systems intended to be included within the scope of thepresent invention include, by way of example only, wireless local areanetworks (WLAN) devices and wireless wide area network (WWAN) devicesincluding wireless network interface devices and network interface cards(NICs), base stations, access points (APs), gateways, bridges, hubs,cellular radiotelephone communication systems, satellite communicationsystems, two-way radio communication systems, one-way pagers, two-waypagers, personal communication systems (PCS), personal computers (PCs),personal digital assistants (PDAs), and the like, although the scope ofthe invention is not limited in this respect.

Types of wireless communication systems intended to be within the scopeof the present invention include, although not limited to, WirelessLocal Area Network (WLAN), Wireless Wide Area Network (WWAN), CodeDivision Multiple Access (CDMA) cellular radiotelephone communicationsystems, Global System for Mobile Communications (GSM) cellularradiotelephone systems, North American Digital Cellular (NADC) cellularradiotelephone systems, Time Division Multiple Access (TDMA) systems,Extended-TDMA (E-TDMA) cellular radiotelephone systems, third generation(3G) systems like Wide-band CDMA (WCDMA), CDMA-2000, and the like,although the scope of the invention is not limited in this respect.

FIG. 1 illustrates a block diagram of one embodiment of a WLAN. In thewireless local area network (WLAN) system 100 shown in FIG. 1, a firstdevice 110 may include a wireless transceiver 112 to couple to anantenna 118 and to a baseband processor 116. Baseband processor 116 inone embodiment may include a single processor, or alternatively mayinclude a baseband processor and an applications processor, although thescope of the invention is not limited in this respect. Basebandprocessor 116 may couple to a memory 114 which may include volatilememory such as DRAM, non-volatile memory such as flash memory, oralternatively may include other types of storage such as a hard diskdrive, although the scope of the invention is not limited in thisrespect. Some portion or all of memory 114 may be included on the sameintegrated circuit as baseband processor 116, or alternatively someportion or all of memory 114 may be disposed on an integrated circuit orother medium, for example a hard disk drive, that is external to theintegrated circuit of baseband processor 116, although the scope of theinvention is not limited in this respect. Likewise, a second device 120may include a transceiver 122, memory 124, baseband processor 126, andantenna 128. Access point 140 may include a transceiver 142, memory 144,baseband processor 146 and antenna 136.

First device 110 and second device 120 may communicate with access point140 via wireless communication links 132 and 134, respectively. Accesspoint 140 may include at least one antenna 136. Alternatively, accesspoint 140, and optionally first device 110 and second device 120, mayinclude two or more antennas to provide a diversity antenna arrangement,to provide spatial division multiple access (SDMA), or to provide amultiple input, multiple output (MIMO) system, or the like, although thescope of the invention is not limited in this respect. Access point 140may couple with network 138 so that first device 110 and second device120 may communicate with network 138, including devices coupled tonetwork 138, by communicating with access point 140 via wirelesscommunication links 132 and 134. Network 138 may include a publicnetwork such as a telephone network or the Internet, or alternativelynetwork 138 may include a private network such as an intranet, or acombination of a public and a private network, although the scope of theinvention is not limited in this respect.

Communication between user first device 110 and second device 120 andaccess point 140 may be implemented in accordance with one or morewireless standards including, for example, one or more wireless cellularstandards, one or more wireless networking standards, one or more radiofrequency identification (RFID) standards, and/or others. In at leastone implementation, for example, the communication is implemented inaccordance with the Bluetooth short-range wireless protocol(Specification of the Bluetooth System, Version 1.2, Bluetooth SIG,Inc., November 2003, and related specifications and protocols). Otherpossible wireless networking standards include, for example: IEEE 802.11(ANSI/IEEE Std 802.11-1999 Edition and related standards like 802.11n),HIPERLAN 1, 2 and related standards developed by the EuropeanTelecommunications Standards Institute (ETSI) Broadband Radio AccessNetworks (BRAN), HomeRF (HomeRF Specification, Revision 2.01, The HomeRFTechnical Committee, July, 2002 and related specifications),Ultrawideband, and/or others.

In accordance with one embodiment of the invention, access point 140 maybe a multimode access point (MAP) in that access point 140 may allowfirst device 110 and second device 120 to communicate with access point140 even though first device 110 and second device 120 may not becapable of communicating with one another, for example where firstdevice 110 is arranged to communicate using a first wireless standard,such as the IEEE 802.11b/g standards, and where second device 120 isarranged to communicate using a second wireless standard, such as ahigher throughput wireless communication standard directed toward, forexample, operation at or near the 5 GHz frequency of the IEEE 802.11astandard, although the scope of the invention is not limited in thisrespect.

In one embodiment, WLAN system 100 includes multiple devices capable ofcommunicating with first device 110 and access point 140. WLAN system100 may include multiple other devices capable of communicating withsecond device 120 and access point 140. The multiple devices capable ofcommunicating with first device 110 may all communicate using a firstwireless standard, such as the IEEE 802.11b/g standards. The multipleother devices capable of communicating with second device 120 may allcommunicate using a second wireless standard such as a higher throughputwireless communication standard directed toward, for example, operationat or near the 5 GHz frequency of the IEEE 802.11a standard, althoughthe scope of the invention is not limited in this respect.

In accordance with one embodiment, access to the medium is controlled bya media access control (MAC) sublayer of the Data Link Layer asdescribed in a wireless standard. In particular, MAC operations controlwhich devices, AP 140, first device 110 and/or second device 120, caninitiate communications over the medium.

In one embodiment, first device 110, second device 120, and access point140 may be arranged to communicate over an identical or similarfrequency band, for example near 5 GHz, wherein the transceivers 112,122, and 142 of first device 110, second device 120, and access point140, respectively, are arranged to operate on a compatible physicallayer, although the scope of the invention is not limited in thisrespect.

In one embodiment, first device 110 may be a legacy device, operatingaccording to an older wireless standard and second device may be a newlydeveloped device, operating according to a newly developed or newerstandard. According to the newer standard, second device 120 may berequired to receive and process communications according to the older,legacy standard. In such embodiments, first device 110 may not be ableto receive and honor communications according to the newer standard, forexample, a new format wireless medium reservation made by access point140, or may not receive or process medium reservation packets sent bysecond device 120, although the scope of the invention is not limited inthis respect. Additionally, second device 120 may be able to receive andhonor communications according to the older standard, for example, anold format wireless medium reservation made by access point 140, and mayreceive or process medium reservation packets sent by first device 110,although the scope of the invention is not limited in this respect.

Because first device 110 cannot process communications from seconddevice 120, protection mechanisms may be used to prevent first device110 and second device 120 from initiating communications that maycollide with communications of the other device. In one embodiment,access point 140 may allow both first device 110 and second device 120to operate with access point 140 and with their peers without requiringa modification to the protocol under which the devices operate, althoughthe scope of the invention is not limited in this respect.

To implement 40 MHz channel switching, for example in the WLAN system100 described with respect to FIG. 1, an Extension Channel informationelement and a Channel Switch Announcement frame may be utilized. In oneembodiment, the Extension Channel information element may include offsetinformation corresponding to an extension channel. The Channel SwitchAnnouncement frame may include the Extension Channel informationelement. A base station, such as AP 140 of FIG. 1, that receives theChannel Switch Announcement may determine control and extension channelsin a 40 MHz channel.

In general, a wireless communication may be classified as IndependentBasic Service Set (IBSS) or the Basic Service Set (BSS). The IBSS isthose wireless networks in which an AP may help identify the remoteclients. The BSS is those wireless networks of an ad hoc nature in whichno APs are provided. A 40/20 MHz capable BSS/iBSS device is one that maysupport a 20-MHz extension channel and a 20-MHz control channel in asingle 40-MHz channel.

In one embodiment, a New Extension Channel Offset element may beutilized by an AP in a BSS or a mobile station (STA) in an IBSS togetherwith a Channel Switch Announcement element when changing to a new (e.g.,40 MHz) channel. One embodiment of a New Extension Channel Offsetelement is illustrated in FIG. 2. In one embodiment, each field 210,220, 230 illustrated in FIG. 2 is an octet; however, any field size maybe supported.

In one embodiment, the New Extension Channel offset field 230 mayindicate the position of the extension channel relative to the controlchannel. For example, a value of “1” may indicate that the extensionchannel is above the control channel, a value of “2” may indicate thatthe extension channel is below the control channel, and a value of “0”may indicate that no extension channel is present. Alternate indicationsmay also be used. In one embodiment, the New Extension Channel Offsetelement 200 may be included in a Channel Switch Announcement frame andalso may be included in Beacon frames and Probe Response frames.

Layers within a wireless communication architecture communicate witheach other via service primitives having, but not limited to, thefollowing forms:

(1) Request A layer uses this type of primitive to request that anotherlayer perform a specific service of scheduling a channel switch andannounce this switch to peer entities in the BSS;

(2) Indication A layer uses this type of primitive to indicate toanother layer that a significant event has occurred. This primitiveindicates that a channel switch announcement has been received from apeer entity; and

(3) Response A layer uses this type of primitive to complete a procedureinitiated by an indication primitive. This primitive is used to schedulean accepted channel switch.

Particularly, in embodiments of the present invention, such primitivesmay be utilized when implementing 40 MHz channel switching.

FIG. 3 is a conceptual illustration of one embodiment of a channelswitch request primitive 300. In one embodiment, the channel switchrequest 300 is a primitive used for requesting a 40 MHz channel switch.Channel switch request primitive 300 may include mode 310, channelnumber 320, new extension channel offset 330, and channel switch countfields 340.

The channel switch request primitive 300 is generated by a systemmanagement entity (SME) to schedule a channel switch and announce thisswitch to peer entities in the IBBS/BBS. Mode 310 is defined in aChannel Switch Announcement element. Channel Number 320 is the newchannel number being switched to. New Extension Channel Offset 330 isthe same as New Extension Channel Offset element 230 of FIG. 2. Thisparameter provides the position of the extension channel in relation tothe control element. In one embodiment, a 40/20 MHz capable BSS/IBSSdevice may insert the New Extension Channel Offset parameter 330 intochannel switch request 300. Channel Switch Count 340 identifies thenumber of Target Beacon Transmission Time (TBTTs) until the channelswitch event as described by the Channel Switch Announcement element.

FIG. 4 is a conceptual illustration of one embodiment of a channelswitch indication primitive 400. In one embodiment, the channel switchindication primitive 400 is a primitive used for indicating that a 40MHz channel switch announcement has been received from a peer entity.Channel switch indication primitive 400 may include peer MAC address410, mode 420, channel number 430, new extension channel offset 430, andchannel switch count field 450.

Peer MAC address 410 identifies the address of a peer MAC from which achannel switch frame is received. Mode 420 identifies the mode asdefined in the Channel Switch Announcement element. Channel number 430indicates the new channel number. New Extension Channel Offset 440 isthe same as New Extension Channel Offset element 230 of FIG. 2. Thisparameter provides the position of the extension channel in relation tothe control element. In one embodiment, a 40/20 MHz capable BSS/IBSSdevice may insert the New Extension Channel Offset parameter 440 intochannel switch request 400. Channel Switch Count 450 identifies thenumber of TBTTs until the channel switch event as described by theChannel Switch Announcement element.

FIG. 5 is a conceptual illustration of one embodiment of a channelswitch response primitive 500. In one embodiment, the channel switchresponse primitive 500 is a primitive used for completing a 40 MHzchannel switch procedure initiated by an indication primitive, such asindication primitive 400 described with respect to FIG. 4. Channelswitch response primitive 500 may include mode 510, channel number 520,new extension channel offset 530, and channel switch count field 540.

Mode 510 identifies the mode as defined in the Channel SwitchAnnouncement element. Channel number 520 indicates the new channelnumber. New Extension Channel Offset 530 is the same as New ExtensionChannel Offset element 200 of FIG. 2. This parameter provides theposition of the extension channel in relation to the control element. Inone embodiment, a 40/20 MHz capable BSS/IBSS device may insert the NewExtension Channel Offset parameter 530 into channel switch request 500.Channel Switch Count 540 identifies the number of TBTIs until thechannel switch event as described by the Channel Switch Announcementelement.

While the invention has been described in terms of several embodiments,those skilled in the art will recognize that the invention is notlimited to the embodiments described, but can be practiced withmodification and alteration within the spirit and scope of the appendedclaims. The description is thus to be regarded as illustrative insteadof limiting.

1. A method comprising: generating channel offset informationcorresponding to an extension channel within a channel of a wirelesscommunications protocol; and transmitting the channel offset informationas part of channel information to be transmitted to one or more remotedevices communicating according to the wireless communications protocol.2. The method of claim 1 wherein the wireless communications protocolcomprises an IEEE 802.11 specification/standard.
 3. The method of claim2 wherein the IEEE 802.11 specification standard comprises IEEE 802.11n.4. The method of claim 1 wherein the channel offset information istransmitted in a Channel Switch Announcement.
 5. The method of claim 1wherein the channel offset information is transmitted in at least one ofa Beacon Frame and a Probe Response Frame.
 6. The method of claim 1wherein the extension channel comprises a 20 MHz channel within a 40 MHzchannel of the wireless communications protocol.
 7. The method of claim6 wherein the 40 MHz channel further comprises a 20 MHz control channel.8. The method of claim 1 wherein the channel offset informationindicates whether the extension channel is at a frequency higher than acontrol channel or a frequency that is lower than the control channel.9. The method of claim 8 wherein the channel offset informationindicates that the extension channel is not present.
 10. Acomputer-readable medium having stored thereon instructions that, whenexecuted, cause one or more processors to: generate channel offsetinformation corresponding to an extension channel within a channel of awireless communications protocol; transmit the channel offsetinformation as part of channel information to be transmitted to one ormore remote devices communicating according to the wirelesscommunications protocol.
 11. The article of claim 10 wherein thewireless communications protocol comprises an IEEE 802.11specification/standard.
 12. The article of claim 11 wherein the IEEE802.11 specification standard comprises IEEE 802.11n.
 13. The article ofclaim 10 wherein the channel offset information is transmitted in aChannel Switch Announcement.
 14. The article of claim 10 wherein thechannel offset information is transmitted in at least one of BeaconFrame and a Probe Response Frame.
 15. The article of claim 10 whereinthe extension channel comprises a 20 MHz channel within a 40 MHz channelof the wireless communications protocol comprising a 20 MHz controlchannel.
 16. An apparatus comprising: control circuitry to generatechannel offset information corresponding to an extension channel withina channel of a wireless communications protocol; and transmit circuitrycoupled with the control circuitry to transmitting the channel offsetinformation as part of channel information to be transmitted to one ormore remote devices communicating according to the wirelesscommunications protocol.
 17. The apparatus of claim 16 wherein thewireless communications protocol comprises an IEEE 802.11nspecification/standard.
 18. The apparatus of claim 16 wherein thechannel offset information is transmitted in a Channel SwitchAnnouncement.
 19. The apparatus of claim 16 wherein the extensionchannel comprises a 20 MHz channel within a 40 MHz channel of thewireless communications protocol.
 20. The apparatus of claim 16 whereinthe channel offset information indicates whether the extension channelis at a frequency higher than a control channel or a frequency that islower than the control channel.